Our objective is to determine whether an imbalance in salt- retaining and salt-losing steroid hormones is casually associated with the development of hypertension in man, especially low renin essential hypertension (LRH). Plasma concentration of most of the steroids known to have an influence on sodium metabolism will be measured by radioimmunoassay under normal physiological conditions and after experimental maneuvers designed to bring out abnormalities in steroid production and metabolism, i.e., after administration of ACTH, angiotension, dexamethasone, metyrapone, glutethimide, and spironolactome and after salt-restriction and loading. Blood production rates will be measured for most of these steroids in addition to plasma concentrations. Data from patients with LRH who respond to therapy will be compared with similar data from non-responders in an attempt to develop a steroid profile to be used in diagnosis and the evaluation of the effectiveness of therapy.